Gut Flora, Disease and Obesity

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The health of your gut flora (the interacting trillions of bacteria of a couple of hundred different species that make up the pound of bacteria that you carry primarily in your large intestines) is more important than your genetics to your overall health.  Thus, your health is a result of diet, gut flora adapted to your diet and exercise.  Everything else, your genetic risks, environmental toxins, etc. are of only minor impact.

I am trying to paint the big picture of how the food that you eat and your gut flora interact to determine your health, by which I mean whether you get sick, become obese and/or bloat with gas.

Health Depends on Gut Flora

If you are healthy, you have a couple of hundred different species of bacteria that help you to digest the protein, fats and carbs that you eat in meat and vegetables.  Your body easily digests protein and fats in meat, fish, eggs and dairy, because enzymes to digest them are present in your stomach and small intestines.  The only carbs that your body can digest are some simple sugars and starch.  The rest of the polysaccharides present in plants cannot be digested without the help of bacteria.  The polysaccharides that your gut flora can digest are fermentable, soluble fiber, e.g. resistant starch, pectin, inulin, arabinogalactan, xylans, beta-glucan, etc.  If you can’t digest soluble fiber, because you have damaged gut flora, dysbiosis, and are missing essential bacterial species normally found in a healthy gut, then the soluble fiber just passes through as insoluble fiber and readily dehydrates into hard, constipated stools.  Partial digestion due to just a few missing bacterial species produces the symptoms of food intolerances.  

Constipation Results from Dysbiosis

The bottom line is that the volume of healthy, soft, firm stools is made up of gut flora that digested dietary soluble fiber and converted it into more bacteria.  If you eat more soluble fiber, this food for your gut flora, will produce proportionately more bowel movements.

Gut Flora Guide Immune System Development

Most of cells of your immune system are in the lining of your gut and there are particular species of gut bacteria directly involved in the development of immune cells that have different functions as they spread throughout your body.  Some of these cells are aggressive and attack pathogens, while others make sure that the aggression doesn’t get out of control and cause autoimmune diseases or allergies.

Gut Flora Divided into Groups to Show Involvement in Disease

Recent studies have demonstrated the role of gut bacteria in producing nutrients, vitamins and neurotransmitters.  To highlight the essential role of gut flora in disease, I have divided the hundreds of species of gut bacteria into groups to illustrate their direct involvement in development of the immune system and regulation of the flow of dietary nutrients involved in obesity.  A recent study shows that an infection can produce a change in gut flora associated with marshaling additional fatty acid nutrients for the host instead of just producing more gut flora.  Chronic change of gut flora in this way leads to obesity.  Other types of dysbiosis contribute to infections, cancer, autoimmune disease, allergies, food intolerances, gas and bloating.

Group A Bacteria  Provide Aggressive Immunity

There are several dozen species of bacteria in healthy gut flora, including the filamentous bacteria, that trigger the development of the aggressive part of your immune system that attacks pathogens, and kills cells of your body that are infected with viruses or are cancerous.  Most antibiotics don’t permanently damage this group of bacteria, so after a course of antibiotics you can usually still stop infections.  Excessive suppression of aggressive immunity contributes to cancer.

Group B Bacteria Provide Suppressive Immunity

There are dozens of other species of bacteria, including Clostridia, that control the development of the suppressive half of your immune system that produces immune cells, such as regulatory T cells, Tregs, that stop the aggressive cells of your immune system from attacking your own cells and innocuous things such as food and pollen.  Many common antibiotics damage these species of bacteria and are thought to contribute to the development of autoimmune diseases and allergies.  Inflammatory bowel disease is characterized by a simplified gut flora with only half the healthy number of bacterial species.  Resistant starch preferentially feeds these bacteria to enhance suppressive immunity and in some individuals cure autoimmune disease.

Group C Bacteria Convert Soluble Fiber to Short Chain Fatty Acids (SCFA)

The fermentable soluble fiber in your diet is typically from vegetables and it is converted by the largest and most diverse group of bacterial species into short chain fatty acids.  Each different plant polysaccharide, and there are hundreds, requires many enzymes for complete digestion to the simple molecules used by the bacteria to make its own proteins, fats and polysaccharides.  Absence of bacteria that are specialized for the digestion of particular polysaccharides or other dietary components can disrupt gut flora and cause digestive disturbances that are experienced as food intolerances (also confused with food allergies that are rare.)  Some of the bacterial species convert polysaccharides into butyric acid and other short chain fatty acids that are the major source of energy for cells that form the lining of the intestines.  These SCFAs are also a major food source for other gut bacteria.

Group D Bacteria Convert SCFAs to Fecal Bacteria to Produce Bulk of Bowel Movements

In healthy people, the SCFAs produced by gut flora feed the intestines and the remainder produced in the large bowel is converted into more gut bacteria, which forms soft stools.  Antibiotics typically damage these bacteria and result in constipation.  These bacteria are typically more sensitive to antibiotics than those that digest the soluble fiber and produce SCFAs, so the excess SCFAs pass into the blood stream and contribute to obesity instead of stools.  Lean mice with gut flora exchanged from obese mice, become obese.  Cattle are fed antibiotics to enhance the conversion of corn polysaccharides into SCFAs and body fat prior to slaughter.

Group E Bacteria convert Soluble Fiber to Methane and Hydrogen, Bloat

Increased volume of the intestines, bloating, results from conversion of soluble fiber into methane, hydrogen and carbon dioxide gases.  Some of this gas is absorbed into the blood and can pass from the large intestines, through the blood, and back to the stomach and small intestines.  Helicobacter pylori, the cause of stomach ulcers and gastric cancer, can utilize hydrogen from the blood as an energy source.

In Summary:

A+B+C+D = healthy, normal weight

A+C+D = normal weight, autoimmunity and allergies

B+C+D = normal weight, susceptibility to cancer, chronic Lyme disease, food poisoning

A+B = normal weight, constipated

A+B+C = obese, constipated

A+B+D = normal weight, food intolerances

A+B+C+E = obese, constipated, bloated

Cure for Dysbiosis and Associated Diseases is Repair of Gut Flora

The excitement about the use of resistant starch (RS) and probiotics with Clostridia and other soil bacteria to reverse the symptoms of autoimmune diseases is based on the ability to repair gut flora damaged by poor nutrition and antibiotics.  Low carbohydrate diets that do not provide soluble fiber to feed gut flora lead to dysbiosis and chronic diseases.  Resistant starch, as the name suggests, passes on to the colon by avoiding digestion with amylases in the small intestines and acts as a soluble fiber to feed gut flora in the colon.  Clostridia convert the RS to sugars and SCFAs usable by other gut flora.  Note that some species of Clostridia produce toxins and it is these pathogens that take over in hospitals after the healthy species are killed off with antibiotics.  Fecal transplants are the best treatment for these hospital acquired infections. 

 I have discussed the role of hygiene, muddy veggies, fermented foods, etc. in several other posts on repair of gut flora.  

Complete repair of gut dysbiosis is possible, but it requires more than just changes in diet and dairy probiotics, as typically recommended erroneously by the medical industry.

Health is dependent on:

1. an Anti-Inflammatory Diet,
2. gut flora adapted to your diet
3. exercise and
4. adequate sleep

The rest (genetics, vegan vs. paleo, environmental toxins, organic veggies, GMOs, etc.) are minor contributors, less than 10% in aggregate, to overall health.

ref.

Gut microbiota composition correlates with changes in body fat content due to weightloss 

Helminths, Oligosaccharides and Immunotolerance

Parasitic worms reverse allergies and autoimmune diseases using oligosaccharides to mimic self and silence immune over-responsiveness.

Helminth therapy, i.e. infection with parasitic intestinal worms to provide remission from allergies, inflammatory bowel and other autoimmune diseases, has been examined as a potential therapeutic model to rehabilitate immunological dysfunction.  The surface oligosaccharides of these worms have been found to mimic human oligosaccharides and alter immune responses by binding to carbohydrate-binding, i.e. lectin, receptors.

Immune Tolerance
The essence of allergic and autoimmune diseases is a defect in distinguishing between pathogen, innocuous and self molecules.  Heightened immune reactions as a result of inflammation move the immune system toward production of antibody and T cell receptors specific for antigens.  Those antigens respond to unique receptors on the surface of each B and T lymphocyte.  The lymphocyte population has been previously depleted of cells that can produce receptors that will bind to most self antigens.  This depletion makes the lymphocyte population generally non-responsive, or tolerant to self antigens.  Thus, the immune system is blind to the body.

Regulatory T Cells and Tolerance
Most of the immune cells of the body are present in the lining of the gut.  It is in the gut that various immune cells continue to develop for their various roles, including controlling immune reactions to self antigens and to common food molecules.  Immune cells in the gut are exposed to some food molecules and bacteria that leak through the cells of the intestinal villi.  Responding to these common antigens by inflammation can lead to inflammatory bowel disease.  This pathological over-responsiveness is normally avoided by development of regulatory T cells, Tregs, that suppress immune responses to common food molecules and to surface antigens of common bacteria.

Treg Development Depends on Gut Flora
Gut bacteria are needed for the normal function of the immune system.  Oddly, Helicobacter pylori, Hp, the cause of stomach ulcers and cancer, also stimulates the development of Tregs.  Thus, the pathology of Hp may result not from its presence, but rather from how it is growing.  Since Hp uses hydrogen gas produced by Klebsiella in the lower bowel and hydrogen production is dependent on dietary starch, then it follows that the pathological behavior of Hp may be dependent on dietary starch.  A low starch diet may actually result in Treg stimulation from Hp and a reduction in allergies and autoimmune diseases.

Tregs Enhanced by Heliminths
Immunological tolerance is also stimulated by parasitic worms, Helminths.  Helminth infestations, therefore, reduce allergies and autoimmune diseases and may contribute to the hygiene hypothesis to explain the prevalence of allergies, autoimmune and other inflammation-based degenerative diseases in modern societies.  Examination of worms to find the molecules responsible for inducing immunological tolerance has identified complex surface and secreted oligosaccharides (small sugar chains) as the active molecules.  Helminth oligosaccharides mimic human cell surface oligosaccharides and bind to carbohydrate-binding, lectin, receptors on immune cells to stimulate Treg development.

Lectin Receptors Control Tolerance
There are many implications of the modulation of the immune system via oligosaccharides.  Note that related oligosaccharides are components of human milk and prepare the gut and develop the immune system.  This explains why formula, which lacks these unique oligosaccharides, results in aberrant gut flora, contributes to neonatal necrotizing colitis and supports the development of allergies and autoimmune diseases.  In contrast, judicious use of self or Helminth oligosaccharides may provide a means of restoring the function of damaged immune systems and therapy for allergies and autoimmune diseases.  Also note that the critical use of lectins, which have oligosaccharide-binding sites rich in aromatic amino acids to bind the hydrophobic faces of the sugars, will also bind and provide entry into immune cells for allergens and autoantigens that have triplets of basic amino acids.  The binding sites of lectins should also bind many aromatic phytochemicals.  Immunomodulation by phytochemicals may result from interference with or mimicking the binding of oligosaccharides to lectin receptors.

reference:
van Die I, Cummings RD.  Glycans modulate immune responses in helminth infections and allergy.  Chem Immunol Allergy. 2006;90:91-112.

Biofilm Transformation, Helicobacter, Klebsiella

Helicobacter pylori causes stomach cancer, but it feeds on hydrogen gas produced by Klebsiella pneumoniae in gut biofilms. DNA released by biofilm bacteria not only transfers antibiotic resistance, but it also provides protection against host antibacterial peptides, such a cathelicidins and defensins.

Exploding Labs

When I was working on host/pathogen interactions and plant disease resistance, I also became familiar with research on the formation of the plant equivalent of cancer, crown galls, and symbiotic bacterial nitrogen fixation. I mention this, because this also exposed me to the free-living bacterial nitrogen fixing system in Klebsiella and to the memorable urban legion of exploding labs. As the story goes, as bacteria convert atmospheric nitrogen gas into ammonia, nitrogen fixation, they use high energy electrons, e.g. from ferrodoxin, and lots of ATP, but they also produce hydrogen gas. In labs where they are researching nitrogen fixation, the excess hydrogen gas would accumulate on the ceiling until... boom! Now those labs are properly vented.

Helicobacter Uses Hydrogen as an Energy Source

Helicobacter pylori is considered the most common bacterial pathogen of humans and is the primary cause of ulcers and stomach cancer. H. pylori lives in the stomach by neutralizing stomach acid with ammonia. Another interesting ability of this bacterium is its ability to use hydrogen dissolved in circulating blood as an energy source. The high energy electrons from molecular hydrogen are transported to its electron transport chain, and the energy is used in membrane transport and ATP production. The circulating hydrogen is produced by gut bacteria.

Klebsiella Is not just a Soil Bacterium, Gut Gases

Klebsiella pneumonia is a lung pathogen and it also forms gut biofilms. Presence in the gut and the ability to produce hydrogen gas has some implications for hydrogen utilizing bacteria like H. pylori. Clearly, the stomach of someone with an abundant source of hydrogen fuel in their blood is a better target for H. pylori colonization. This explains why even at age 50, individuals who were exclusively breastfed have a lower incidence of H. pylori and stomach cancer, since even a single bottle of formula can shift an infant to adult, i.e. Klebsiella gut flora.

Klebsiella Needs Carbs to Produce Hydrogen

K. pneumoniae has been associated with Crohn’s Disease and Ankylosing Spondylitis. It grows in gut biofilms and produces pullulanase, an enzyme that can utilize the branched glucosides left over from the action of amylase on plant starch. So K.p. has an untapped food source and it needs lots of ATP to produce hydrogen gas. The nitrogenase needed for nitrogen fixation and hydrogen production is very sensitive to oxygen, so this means that K.p. needs a partially anaerobic environment and must get its energy from fermentation. Fermentation yields much less ATP than respiration using oxygen, which means that K.p. can only produce hydrogen with lots of glucose from starch.

Low Carb Diet Cures Crohn’s Disease

It turns out that the antigen causing Crohn’s disease is the pullulanse (with collagen mimetics.) As you should expect, it has a basic triplet. Eating a low carb diet reduces the flareups of Crohn’s disease, presumably by starving out the K.p.. It is interesting that nitrogenase is the antigen involved in Ankylosing Spondylitis.

Biofilms Promote Transformation and Antibiotic Resistance

Just as a footnote to the benefit of K.p. as a citizen of a biofilm community, H.p. should also live in those biofilms, since that is the source of the hydrogen it uses. Biofilms also stimulate the exchange of DNA, because the quorum sensing chemical signals trigger the release of DNA. The DNA is a component in the matrix that binds bacteria in the biofilm and can work in conjunction with bacterial acidic polysaccharides and host heparan sulfate. These acidic polymers tend to bind the basic antimicrobial peptides, e.g. defensins and cathecidins produced as a major non-adaptive defense against bacteria. Thus, the release of DNA triggered by quorum sensing, builds matrix, facilitates DNA transformation that is the foundation for the spread of antibiotic resistance in gut biofilms and provides resistance against antimicrobial peptides.